This astrolabe, attributed to Gerard Mercator, contains six tympanums for latitudes 43°, 36°, 39° and 42°, 45° and 48°, 51° and 54°, and 57° and 60° (corresponding to the regions between North Africa and Sweden); a seventh tympanum carries the geographic mirror for the northern and southern hemispheres. Probable provenance: Robert Dudley bequest to the Medici collections.